Service: Longines Ultra Chron 8309 calibre 431

IMG_1900At least the broadband connection at home works, so I can write a little blog entry about this watch. Tintin from Thailand sent it in, and it’s probably the best UltraChron I’ve seen in this workshop. It’s in almost mint condition…

I love the 431 movement. Fast beating at 36,000 b.p.h, and built with the usual Longines quality. Great design, and I would wear this watch very happily indeed.IMG_1901

The condition of the case back is remarkable. The watch looks totally new old stock.IMG_1903

The dial is impeccable. Not the slightest mark, and as good as new.IMG_1905Still a remarkable performance considering the movement is totally dry, and that it’s so fast beating! But the amplitude is low, so a service is well in order.IMG_1906

The 431 is not only technically well made, it also looks very nice indeed.IMG_1907

The rotor is screwed to the automatic device bridge with a screw and two washers, which I find a bit unnecessary. In the end, you just want the inner ring of the rotor bearing to be tightly screwed to the bridge, and all other manufacturers achieve that with a single screw. Only Longines needs a screw and two washers 😉IMG_1910

The base movement. The shock system is a KIF, with its tell-tale shock spring design.IMG_1913

The gear train.IMG_1917

The 431 has a super date change, which is as snappy as a Zenith on a good day. A slow power build-up guarantees that there is minimal impact on beat rate and amplitude during the date change.IMG_1919

Simple, but very effective.IMG_1924

Did you say “Do not open?”IMG_1925

Oopsy. As the power reserve is a bit low, I am fitting a new mainspring. The original isn’t available any more (no complete barrel, no mainspring), but I find a very close 0.95 x .15 x 340 x 11.2.IMG_1926

Everything goes into the cleaning machine.IMG_2031

The new mainspring for the barrel.IMG_2032

The gear train goes in.IMG_2033

Look at the condition of all the screw heads and the plate. Not a single scratch, no marks, nothing!IMG_2034

Just put together, this is looking very good, and we have a decent amplitude.IMG_2035

What a beauty.IMG_2036

The automatic device is back together. Marvel at the condition.IMG_2037

Utterly pristine.IMG_2038Not a mark on the case either, and I really really would love to own this watch. Lucky Tintin!



15 thoughts on “Service: Longines Ultra Chron 8309 calibre 431

  1. Hi Christian, I’m working on Longines 431 and I need a new clutchweel for automatic. Can You help me or maybe suggest a adress for me…. I have only the very thin washer between rotor and the shrew. Can you help me?
    Yours sincerely
    Watchmaker Heidi Pettersen

  2. Hello Christian,
    I’m Claude.
    Very interesting work ! I am amazed, nice.
    I am the owner of an ultra-chron too. I have two questions.
    1- When I put it off the whrist, it still working for an hour or two. Do I have to change the mainspring ? Subsidiary question, where can I find it ?
    2-On the dial, there is the mention “automatique” for your type of ultra-chron and “Automatique” for mine. Is it an indication of the period of production ? Do you know that ? May be earlier for your’s.
    Glad to visit your site.
    Best regards

      • h
        Hi Christian,

        Thank you for the quick answer ! I am looking now for a clock service in my région (Chambéry-Grenoble).Do you have an advice ? I know it would be better with you, but your workshop is far away.

        Best regards

  3. Hi Christian – I particularly enjoyed this post as you serviced my almost identical watch a few weeks ago (now keeping perfect time, thanks!). My watch is not in such good general condition, but the mainspring didn’t appear to need changing – any idea why this might be? Does NOT being used, as presumably this watch hasn’t been much, cause the mainspring to deteriorate?

    • The decision to change the mainspring goes as follows: if there is an original available, it’s a no-brainer, and I will always change it. If I can only get a mainspring that isn’t exactly the original size, I will leave the original mainspring. If the original is bent or “tired”, I will change it for the closest match available.

  4. Very nice indeed!
    My only problem with owning such a NOS condition watch would be that I would never wear it in fear of inflicting any damage to it….

    • Only thing to do is….buy two so that you can wear one of the less tidy examples.

      Very nice indeed Tintin.

      I do like Longines.

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